In an external-heat engine, the heat source is located outside the external-heat engine, which is arranged to convert heat into mechanical energy, for example. This invention relates to an external-heat engine that works primarily on the so-called Organic Rankine Cycle (ORC). It is assumed that it may also be suitable for other external-heat engine cycles, and then in particular a conventional Rankine cycle. This process, in its simplest form, includes heating a medium in an evaporator until it takes a vapour phase under pressure. Then the vapour is carried into the external-heat engine where the pressure is reduced while the thermal energy is converted into mechanical energy. The medium is then condensed in a, relative to the external-heat engine, external condenser before it is pumped back into the evaporator.
The invention is directed towards an external-heat engine of the piston type.
External-heat engines of this kind are designed to be in continuous operation day and night for several years without any repairs and with minimal maintenance. Things such as seal design and choice of driving lines have turned out to be critical to achieving a sufficiently long life.
The driving lines used the most for valves in conventional piston engines usually include chain or toothed-belt operation. Known driving lines of this kind do not have sufficiently long lives for use in an external-heat engine.
However, it has turned out that a geared drive, even with its negative characteristics such as noise and vibration transmission, constitutes a usable solution. The reason is a substantially longer life under suitable conditions. Correct dimensioning and good lubrication are critical in that respect.